Jeremy Hunt, the Health Secretary, is in line for a windfall worth more than £15m from a company sale that would propel him to the top of the Cabinet rich list.

Sky News can exclusively reveal that Hotcourses, an education listings service set up by Mr Hunt 17 years ago, is in detailed negotiations about being sold to Inflexion Private Equity, an investment firm, for about £35m.

Mr Hunt is understood to own 49% of Hotcourses, meaning that his shareholding would be worth just over £17m if the takeover is completed.

News of the prospective windfall for Mr Hunt, the MP for South West Surrey, may cause embarrassment for the Government at a time when a debate about the cost of living is dominating Britain's political discourse.

With the NHS expected to face a strain on resources during the winter, Mr Hunt is likely to face a tough few months in Westminster.

Ed Miliband, the Labour leader, has frequently sought to portray the Conservative-led coalition as an out-of-touch millionaires' club, and Mr Hunt is far from the only independently wealthy Cabinet minister.

Prime Minister David Cameron, Chancellor George Osborne, Foreign Secretary William Hague and Defence Secretary Philip Hammond are all said to have amassed multimillion pound fortunes.

Jeremy Hunt set up the company after working in Japan

However, a £35m sale of Hotcourses would also cement Mr Hunt's status as one of the most successful entrepreneurs to have forged a parliamentary career in recent times, during a period when politicians are frequently accused of having inadequate experience of the business world.

Private equity insiders said that Inflexion had outbid a number of other buyout firms to win a period of exclusivity in which to finalise an agreement. The roughly £35m price-tag is higher than previous estimates of Hotcourses' value.

It was unclear on Friday when the exclusivity period ends, but a source close to the transaction said it was unlikely to be announced for at least a few weeks.

"It could still fall through. It's not a done deal," they said.

Hotcourses was set up in 1996 by Mr Hunt and his business partner, Mike Elms, and provides listings information about evening, training, university and other courses.

Now employing more than 200 people, Mr Hunt established the business when he returned to the UK after two years in Japan teaching English and learning Japanese.

It now claims to be the world's largest course database, advertising more than 700,000 courses and 33,995 scholarships from more than 27,000 institutions.

According to accounts filed at Companies House for the six months to July 31, 2012, the company had a turnover of £6.5m, generating pre-tax profits during the period of just under £2m.

The Health Secretary, who turned 47 last week, has received several million pounds in dividends since Hotcourses was founded.

An aide to Mr Hunt refused to comment on the deal or on the size of his shareholding, but a person close to him insisted that he was not playing any role in the sale negotiations.

The latest Register of MPs' Interests confirms that the Health Secretary remains an investor in Hotcourses but does not disclose the size of his interest.

The company's website lists Mr Hunt as a member of its management team but states that he "stepped aside from all management responsibilities at Hotcourses Ltd in order to focus on his parliamentary duties, and is no longer involved in the running of the company".

It is unclear when Mr Hunt would receive the money from the sale of the company or whether he would remain as an investor under new owners.